Field of the Invention
This invention relates to a method of manufacturing a center electrode for a spark plug in which a spark-erosion resistant firing tip is welded to a front end of a center electrode.
In a spark plug for an internal combustion engine, a firing tip is welded to a front end of a center electrode. It is known that the tip is made of a noble metal such as platinum-based alloy to impair a spark erosion property with the front end of the center electrode.
It is considered to diametrically reduce the firing tip in order to maintain good sparking or ignitability condition of the spark plug. The diametrically reduced tip, however, exceedingly rises its temperature to accelerate its spark erosion by oxidation-evaporation and dispersion, although it advantageously concentrates spark discharge to lower the spark discharge voltage.
Therefore, the invention is made on the basis of the concept that a heat-conductor core is enclosed in a nickel-alloyed metal so as provide an heat escape path from the firing tip to the heat-conductor core, thus preventing the temperature of the firing tip from exceedingly rising.
It is an object of the invention to provide a method of manufacturing a center electrode for spark plug in which a firing tip is provided in thermally transferable relationship with the heat-conductor core, thus effectively preventing the firing tip from being worn so as to contribute to an extended service life with minimum cost.